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Date: Fri, 29 Mar 2024 17:37:45 -0700
From: Kees Cook <keescook@chromium.org>
To: Jonathan Corbet <corbet@lwn.net>,
	Andrew Morton <akpm@linux-foundation.org>
Cc: Lasse Collin <lasse.collin@tukaani.org>, Jia Tan <jiat0218@gmail.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 00/11] xz: Updates to license, filters, and compression
 options
Message-ID: <202403291736.B7E9C61@keescook>
References: <20240320183846.19475-1-lasse.collin@tukaani.org>
 <202403291221.124220E0F4@keescook>
 <87h6go3go2.fsf@meer.lwn.net>
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In-Reply-To: <87h6go3go2.fsf@meer.lwn.net>

On Fri, Mar 29, 2024 at 02:51:41PM -0600, Jonathan Corbet wrote:
> "Kees Cook" <keescook@chromium.org> writes:
> 
> > On Wed, Mar 20, 2024 at 08:38:33PM +0200, Lasse Collin wrote:
> >> XZ Embedded, the upstream project, switched from public domain to the
> >> BSD Zero Clause License (0BSD). Now matching SPDX license identifiers
> >> can be added.
> >> 
> >> The new ARM64 and RISC-V filters can be used by Squashfs.
> >> 
> >> Account for the default threading change made in the xz command line
> >> tool version 5.6.0. Tweak kernel compression options for archs that
> >> support XZ compressed kernel.
> >> 
> >> Documentation was revised. There are minor cleanups too.
> >> 
> >> Lasse Collin (11):
> >>   MAINTAINERS: Add XZ Embedded maintainers
> >>   LICENSES: Add 0BSD license text
> >>   xz: Switch from public domain to BSD Zero Clause License (0BSD)
> >>   xz: Documentation/staging/xz.rst: Revise thoroughly
> >>   xz: Fix comments and coding style
> >>   xz: Cleanup CRC32 edits from 2018
> >>   xz: Optimize for-loop conditions in the BCJ decoders
> >>   xz: Add ARM64 BCJ filter
> >>   xz: Add RISC-V BCJ filter
> >>   xz: Use 128 MiB dictionary and force single-threaded mode
> >>   xz: Adjust arch-specific options for better kernel compression
> >> 
> >>  Documentation/staging/xz.rst    | 130 ++++++++---------------
> >>  LICENSES/deprecated/0BSD        |  23 ++++
> >>  MAINTAINERS                     |  14 +++
> >>  include/linux/decompress/unxz.h |   5 +-
> >>  include/linux/xz.h              |   5 +-
> >>  init/Kconfig                    |   5 +-
> >>  lib/decompress_unxz.c           |  39 ++++---
> >>  lib/xz/Kconfig                  |  13 ++-
> >>  lib/xz/xz_crc32.c               |   7 +-
> >>  lib/xz/xz_dec_bcj.c             | 183 ++++++++++++++++++++++++++++++--
> >>  lib/xz/xz_dec_lzma2.c           |   5 +-
> >>  lib/xz/xz_dec_stream.c          |   5 +-
> >>  lib/xz/xz_dec_syms.c            |  16 +--
> >>  lib/xz/xz_dec_test.c            |  12 +--
> >>  lib/xz/xz_lzma2.h               |   5 +-
> >>  lib/xz/xz_private.h             |  20 ++--
> >>  lib/xz/xz_stream.h              |   7 +-
> >>  scripts/Makefile.lib            |  13 ++-
> >>  scripts/xz_wrap.sh              | 157 +++++++++++++++++++++++++--
> >>  19 files changed, 487 insertions(+), 177 deletions(-)
> >>  create mode 100644 LICENSES/deprecated/0BSD
> >
> > Andrew (and anyone else), please do not take this code right now.
> >
> > Until the backdooring of upstream xz[1] is fully understood, we should not
> > accept any code from Jia Tan, Lasse Collin, or any other folks associated
> > with tukaani.org. It appears the domain, or at least credentials
> > associated with Jia Tan, have been used to create an obfuscated ssh
> > server backdoor via the xz upstream releases since at least 5.6.0.
> > Without extensive analysis, we should not take any associated code.
> > It may be worth doing some retrospective analysis of past contributions
> > as well...
> >
> > Lasse, are you able to comment about what is going on here?
> 
> FWIW, it looks like this series has been in linux-next for a few days.
> Maybe it needs to come out, for now at least?

Yes, for sure. Andrew, just so it's explicitly clear: please remove this
series from -mm for now, until the situation is better understood.

Thanks!

-Kees

-- 
Kees Cook